Typical of electric ignitor probe assemblies are the sparking or discharge type, which require high voltage and fire by charging a capacitor, and the glow plug type which employ high amperage to generate heat. As is known in the art, oil can bring the initial temperature of the boiler into operating ranges relatively quickly after which the boiler can be switched over to a different fuel such as coal.
Irrespective of the fuel, the ignitor must be able to withstand very high temperatures encountered initially by high energy employed for ignition and subsequently, by virtue of being positioned in the midst of the burner flame at least until the boiler operation temperature is reached and in some environments, indefinitely. Boilers of the type contemplated herein are very large dimensionally and hence, the ignitor probe assembly can be positioned ten feet or more into the burner.
Eventually, the ignitor probe will succumb to the high temperature environment and require replacement. A common cause of failure is burn-out of the electrode tip where the spark is generated. Inasmuch as existing ignitor probes are sealed structures in order to provide longer life, the entire probe is discarded. Prior to the present invention the old ignitor probe was removed and discarded, there being no attempt, much less ability, to repair it. Such practices are costly, particularly when a given facility may need to replace a dozen or more probes as frequently as every three months.
Although the problem has existed for a long time, the art has not taught an ignitor probe having a replaceable electrode. At least one early patent, U.S. Pat. No. 1,430,429 describes a spark plug for internal combustion engines that can be disassembled while mounted in the engine for a variety of reasons including priming the engine, releasing compression and replacement of the electrode.
U.S. Pat. No. 3,505,568 provides an ignition device for use in environments such as bakery ovens. One of the features of the device is the provision of a conductor rod in two sections joined by a conductive metal coupling. These elements allow for the replacement of a pitted electrode by disconnection of the rod sections at the coupling and substitution of a new electrode unit.
U.S. Pat. No. 4,309,738 discloses a recent ignitor plug which provides a metal sleeve to hold the electrode firmly within a ceramic insulator to prevent the electrode tip from vibrating during use. The electrode does not appear to be removable from the ignitor.
While the foregoing patents generally provide developments in spark plugs and ignitors, the art has not taught an ignitor probe for oil burning furnaces and like environments that can be removed and disassembled for the replacement of damaged components.